Physical combination of calcium and lithium hydroxy stearates for forming greases



March 22, 1960 WORKED PENETRATION L. W. SPROULE ET AL PHYSICALCOMBINATION OF CALCIUM AND LITHIUM HYDROXY STEARATES FOR FORMING GREASESFiled July 17,- 1957 MIXTURE PREPARED BY CO-SAPONIFICATION LITHIUM SOAPCALCIUM SOAP Lorne W. Sproule Warren C. Poflenden B fa.M

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Inventors Attorney ilnited rates PHYSICAL COMBINATIUN 6F CALCIUM ANDLITHIUM HYDROXY STEARATES FOR FORM- ING GREASES Lorne W. Sproule,Sarnia, Lamhton, Ontario, and Warren C. Pattenden, Courtright, Lambton,Ontario, (1am ada, assignors to Essa Research and Engineering Com pany,a corporation of Delaware Application July 17, 1957, Serial No. 672,4323 Claims. Cl. 252- The present invention is concerned with improvedlubricating greases based on the use of a thickening amount of a novelphysical combination of calcium and lithium 12-hydroxy stearates.

This application is a continuation-impart of Serial No. 316,302,Calcium-Lithium Hydroxy Fatty Acid Soap Greases, filed October 22, 1952,bythe present inventors and now abandoned.

In brief compass, this invention proposes a lubricating greasecomposition comprising a lubricating oil thickened with a greasethickener formed at a temperature in the range of 275 to 315 F. bysaponification of 12-hydroxy stearic acid with a base comprising about20% lithium hydroxide and 80% calcium hydroxide, so that the calcium andlithium soaps are simultaneously formed in a proper ratio to obtain anovel physical combination of the two soaps having propertiesunexpectedly different from the known properties of the individualsoaps. This new physical combination of the soaps is an excellent greasethickener in itself, but it can also be combined with other conventionalgrease thickening soaps, especially with additional amounts of lithiuml2-hydroxy stearate.

As the art of grease manufacturing has become more sophisticated, it hasbeen realized that greases having greatly improved properties over thesimple soap greases could be prepared by judicious combinations ofdilferent basic materials, different soaps of perhaps different chainlengths, configuration and substituent groups, and/or salts, eitherinorganic salts or salts of low molecular weight carboxylic acids. Quiteoften it has been found that such combinations of materials unexpectedlyresult in new types of thickeners, usually broadly termed complexes,which account for the improved properties of the grease products. Thesecomplexes often have properties, such as X-ray diifraction patterns,inconsistent with a mere physical blend of the components and can be ofmany types. It is believed, for example, that the complex formed betweena C or higher carboxylic acid soap and calcium acetate at a temperatureabove 425 F. is of the ionic type, and results in a new crystalline soapstructure. Chemical complexes of various natures are believed to beformed between low molecular weight dicar'boxylic acid salts and soaps.

The art of grease manufacture has not evolved to a point where thesecomplexes are so well known that the tailor making of a product involvesthe simple selection of known ingredients. Extensive experimentation anddevelopment are still called for, and quite often unexpected results areobtained.

Mixed calcium and lithium stearate greases have been known to the art.In order to make a satisfactory grease, the lithium component must bepresent in the thickener in an amount in excess of about wt. percent,which makes the grease excessively expensive. These greases also aredeficient in their mechanical stability and oxidation resistance.

These greases are valued for their high dropping points. Their waterresistance leaves something to be desired, the conventional calciumgreases usually giving better service in the presence of water. In orderto use a minimum amount of thickener in a grease the lithium soaps mustbe prepared at a temperature above 400 F.

Ca l2-hydroxy stearate greases have also been disclosed in the art, andare valued because they do not have to be plasticized with water. Theirdropping points, however, do not exceed 290 F., and they must beprepared at relatively low temperatures in the order of 275 F. It hasalso been found, and this is believed to be un-' appreciative by theart, that calcium 12-hydroxy stearate greases are very water sensitive.They will breakdown and fiuidize in the presence of more than 0.4 wt.percent water when worked at temperatures above about 190 F. This isobjectionable, for example, in equipment such as food can closing unitswherein the grease must lubricate at 200 F. in the presence of condensedsteam.

From this knowledge of the art, it is believed that in the presentinvention, it is unexpected that a superior grease thickener comprisinglithium and calcium soaps in a novel physical combination could beprepared at a relatively low temperature using only 20 Wt. percentlithium through the use of l2-hydroxy stearic acid in" place of theunsubstituted acids. It has also been found that this novel physicalcombination permits a lesser amount of total soap to be used in formingthe grease. This use of such a minor amount of lithium in thethickerror, the use of less thickener, and the lower manufacturingtemperature, are very important from an economic standpoint, as will beappreciated by those skilled in the art.

One unexpected feature of this invention is that the water sensitivityof the calcium 12-hydroxy stearate grease is completely overcome bymodifying it by physically combining it with a minor amount of thelithium soap. It would have been expected that the lithium soap wouldnot improve the water sensitivity of the calcium soap, because thelatter is generally considered to be superior in water resistance. Forexample, lithium oleate will practically dissolve in water, whilecalcium oleate will not.

Another unexpected feature of this invention is that this novel physicalcombination can be prepared at mod erate temperatures in the range of275-315 F. This is above the maximum temperature permissible in themanufacture of the calcium soaps, and well below thehigh temperatures,400 F. necessary to form the lithium soaps. It would have been expectedthat, at this lower temperature, the lithium soap molecules would nothave been sufiiciently mobile to enter into a physical combination.

It must be appreciated that this new physical combina tion of the soapscannot be arrived at by simple blending of the individual soaps, whetheror not this is followed by heating. An unsatisfactory product isobtained by simply blending the components. The two soaps must besimultaneously formed by a co-saponification of the 12-l1ydroxy stearicacid at a temperature in the range of 275-315 F. in order to achieve thedesired physical combination. The two saponifying agents can be addedsimultaneously to the acid solution, or one can be added after theother, so as the saponification because of the first added agent issubstantially complete. The

Lithium l2-hydroxy stearate greases have also been 0 known to the art,but are also excessively expensive.

'two saponifying agents are preferably blended in plant scale operationswith the acid solution within 10 minutes of each other.

lithium soap content, although to permit a little latitude this is givenas being in the range of 18 to 22% in the attached claims. Greateramounts of lithium soap do' not cause the formation of further amountsof the physical combination and the thickener partakes of the propertiesof a blend between the 20% lithium/ 80% calcium physical combination,and the remaining lithium soap that is present. If a lesser amount oflithium soap is used, say 15 wt. percent, the calcium 12-hydroxystearate is not modified sufficiently to overcome the above describedwater sensitivity.

This invention will become clear from the following examples anddescription with reference to the drawing attached to and forming a partof this specification.

The drawing is a graphical presentation of the relation ship between thecalcium and lithium ratio of the soap and the worked penetration of thegrease product, at a total soap content of wt. percent. This graphdemonstrates the formation of thenovel physical combination of snaps ofthis invention.

Greases in accordance with the present invention can be prepared asfollows: IZ-hydroxy stearic acid or an equivalent material is charged toa grease kettle and heated therein to about 180 -200 F., preferably inthe presence of an equal weight of lubricating oil, while stirring. Thelime is then added, preferably in the form of a water slurry whileheating and mixing are continued. After about 1 3-10 minutes, thelithium hydroxide is added, usually as an aqueous solution. The mixtureis then further heated at about 275 to 315 5., preferably 300-310 F.,until dehydration is complete, which can require about 3-6 hours. Ifdesired, further lubricating oil is added as the. grease thickens in thecourse of the dehydration process.

After dehydration is complete, the kettle contents are cooled whilestirring. Oil is added while cooling progresses until the desired soapcontent is reached. It has been found that this soap content need notexceed wt. percent and is usually below 10 wt. percent for a greasebased on the novel physical combination of soaps alone.

After oiling the grease back, the grease can be finished by working ormilling, as in a Manton-Gaulin homogenizer or Morehouse mill. After orduring milling, further oil can be added, if desired, to bring theworked penetration up to the final desired value.

As mentioned before, the new physical combination of the calcium andlithium 12-hydroxy stearates can be used in combinations with otherconventional grease thickeners. These can be simply blended with thenovel grease thickener of this invention, followed by heating ifdesired. It is especially preferred to blend thecombination snaps ofthis invention with additional amounts, in the range of 15 to wt.percent, of lithium 12-hydroxy stearate to obtain a grease especiallysuitable for the lubrication of railroad car wheel roller bearings. Thisadditional amount of lithium soap in the blend can conveniently beprovided by using an excess of the lithium saponifying agent during theco-saponification step, or by blending the physical combination of soapsof this invention with additional lithium soap.

EXAMPLE 1 A grease containing less than 12 wt. percent of mixedlithium-calcium 12-hydroxy stearate soap thickener having a lithium tocalcium soap ratio of 20:80 was prepared a slurry in pounds of water.About 5 minutes later the 4 was checked for free alkali and found to be0.2%. This was considered satisfactory. After heating at 290-300 F. forabout 5 hours, the steam was turned oit and the kettle contents allowedto cool. A test on the grease for water content at this stage wasnegative. While cooling from 300 F. to about 200 F'., 1181 pounds ofmineral oil were slowly added, along with 10 pounds ofphenylalpha-naphthylamine dissolved in 10 pounds of oil. The finishedgrease was drawn from the mixer into containers at 190 F. This greaserequired no milling. The composition and properties of the grease aresummarized in "Table I.

Table I Formula, percent by weight:

12-hydroxy stearic acid 10.8 Lithium hydroxide monohydrate 0.36 Hydratedlime 1.26 Mineral oil 1 87.08 Phenyl-alpha-naphthylamine 0.5

Inspections:

Percent soap:

As Li IZ-hydroxy stearate 2.3 As Ca 12-hydroxy stearate Q; i 9.3 Freeacid, percent oleic 0.28 Excess alkali, percent LiOHl-I O 0.1 Workedpenetration, 77 F 275 Mechanical stability, penetration after 10,000

strokes in fine hole Worker 295/ F. Water absorption (mixer method) atF.: No. of ccs. of water absorbed 11 (Consistency good) ASTM droppingpoint, F. 318 Wheel hearing test, 6 hrs. at 220 F. and

60 mph:

Gms. of grease leakage 1.4 Over-all rating Good Spindle test, hrs. at250 F. and 10,000 rpm. 1100 App. viscosity at 100 SPC. 1Z

Shear (Strokes):

77 F. 180 130 F 68 F. 38 200 F. 30 225 F. 23 250 F. 24 275 F. 27

300 F. 9.5 Bleeding-percent 'oil loss after 100 hrs. at 225 Viscosity 60SUS at 210 F., and a. viscosity index or 50.

It will be noted that this grease, in spite of its low total soapcontent and very low lithium soap content, has a satisfactory droppingpoint above 300 F.', excellent working properties, very high waterresistance and excellent bearing performance.

t... EXAMPLE 2 Four additional greases were prepared besides grease A ofExample 1. The three lithium containing greases, B, C, and D wereprepared in a manner similar to that of Example 1 at a saponificationand dehydration temperature of about 300-310 F. Grease E, a 100% calciumgrease, was prepared by melting the acid in four times its weight ofmineral oil at 180 F. A water slurry of the lime was added in sightexcess, and the mixture was then stirred and dehydrated at about 270 F.,the maximum permissible temperature. This required about 14 hours.

when dehydration was complete, further oil was added to adjust the soapcontent. The oil used for these greases 6 ing properties. When thecalcium 12-hydroxy stearate 1s modified, however, in accordance withthis invention,

Table H the properties of the new crystalline structure are such as toyield fibers having good properties. Grease B o D A n 5 EXAMPLE 3Percent Lithium soap in thick Nine additional greases were preparedhaving a total ener 100 40 20 0 Percent mp after oiling back and 4 soapcontent of 10 wt. percent, 1n a base oil similar to w i g g 153 M3 12 51L6 that of Example 1. Products F and G, consisting mostor e pene raiona 77 328 280 280 275 ASTM Dropping Point o F u 331 318 318 1y of thecalcium soap, were of necess1ty prepared at a ASF mi ig somewhat lowertemperature. Table III gives the results 0 greaseconta ing5wt.percentwatermixed atmm tempew and inspections of the grease products F throughN. Ag?? E 3 The attached drawing graphically illustrates by the i.icro-pene ration at"" F. after heating at Fund'r 50 1 dashed line therelat1onsh1p between the llthlllm calcium lbs/sq. in. nitrogen pressure:9 ratio of the greases, and the worked penetration of these After 31mmgg Fluid grease products. The solid line on the graph illustratesAiterfihours as the worked penetration of greases having comparablelithium-calcium ratios, but prepared by simple blending The data ofTable II show the efiect of substituting of the two soaps rather than byco-saponification.

Table III In oo'n' I]; K L M N Percent of Soap which is lithiumG) 0 5 1220 23 40 60 80 100 Worked Penetration 280 284 274 279 281 318 336 373400 Dropping Point 290 292 288 318 320 327 342 364 373 Percent Change inPenetration after 16 hours at 200 F. under 5) lbs. nitrogen pressure(grease mixed with 5% water)- 168 128 71 0 1 F prepared at 265 F.; Gprepared at 280 F.; all other products made at 300310 F. 9 Balance iscalcium.

a minor portion of lithium for the al ium in the hy- Table III and thedrawing clearly illustrate thatthere droxy stearate greases. Grease Brequires substantially more than 15.3% soap in order to obtain a greasehaving a worked penetration of about 280. The amount of soap necessarywould be less if grease B had been prepared at a higher temperature ofabout 400 F.

Greases A and D illustrate the novel physical combination of soaps ofthis invention, and show that only 12.5 Wt. percent or less soap isneeded to achieve the desired penetration. Grease C illustrates thisphysical combination of soaps with an additional 20% thickenercomprising of lithium 12-hydroxy stearate.

For comparison, a grease prepared with stearic acid, rather than thehydroxy acid, having a lithium-calcium ratio of /60 and a total soapcontent of 15 wt. per cent, has a worked penetration of 395. Stearicacid is, therefore, not a suitable ingredient in this type of greaseprepared at 275 315 F.

The last two inspections of Table II give the results of testing thewater sensitivity of the, greases. Grease A was substantially unaffectedby the water, while the 100% calcium grease rapidly fluidized.

A calcium 12-hydroxy stearic grease hardens as the water contentdecreases during the dehydration step. Thus, a calcium 12-hydroxystearic grease containing 20 wt. percent soap and 0.5 wt. percent water,while being dehydrated at 260 F., is semi-fluid. When the water contentis reduced to 0.05%, the Work penetration is 142. The effect of theWater in the ea in iZ-hydror-iy stearic grease is reversible about190-200 F. For eX- ample, if water is mixed With a calcium IZ-hydroxystearic grease at 200 F., it reverts to a fluid product. When, however,20% of the total soap of the grease is formed from lithium 12-hydroxystearate by cosaponification in the manner of this invention, the greaseproduct does not becomefluid when heated in the presence of water above200 F. While the reason for this is not certain, it is believed thatabove 200 F. calcium l2-hydroxy stearate exists as a monohydrate. Thegeometry of this monohydrate crystal is probably such as to form poorfibers having inferior grease thickenis a new type of structure, or newphysical combination, formed by the lithium and calcium 12-hydroxystearic soaps when they are in the ratio of 20% lithiumiand calcium, andwhen they are prepared by co-saponification.

The graph shows the sharp change in the worked penetration of the greaseproducts that occurs when the lithium content reaches about 20%. This isindicative of the formation of the novel physical combination of soapsof this invention.

Examples 2 and 3 together show the remarkable water insensitivityimparted to the calcium 12-hydroxy stearate by properly physicallycombining it with about 20% of the lithium soap, and also clearly showthat the full benefits of this invention are, not obtained by using lessthan about 20% of the lithiumsoap.

EXAMPLE 4 Table IV Grease.. L M

Worked penetration at 77 F 290 295 Drawing Point, "F 288 288 ASTMMicro-penetration at 77 F. of grease containing 5% water, percentincrease 17 16 The attached drawing illustrates the results obtained byblending different amounts of the soaps to obtain several more greases.Comparison ofthe two lines shows that a product having differentphysical properties is pre pared by 'cos'aponificationl .Thisexampleshows that the novel physical combination of soaps, according to thisinvention, cannot be obtained by simple blending of the components,butthat it must be formed by co-sapouification at 275 3l5 F.

EXAMPLE .5

When the amount of lithium saponifying agent used is in excess of thenatural ratio of 20%, the excess lithium soap is simply blended withphysical combination of soaps. This is illustrated by the following: Twogreases were prepared at 300 F., similar to greases F and N of Table111, each having a total soap content of wt. percent. These twogreases,one having 100% lithium soap and the other lithium and 80% calciumsoaps, were then blended at about 100 F. to achieve a grease wherein thethickener comprised 40% lithium soap and 60% calcium soaps. This blendcontained 10 wt. percent of total soap and had a dropping point of 332F. and a worked penetration at 77 F. of 293. Itcan then be seen thatthis blend had properties substantially equivalent or slightly superiorto the 'cosaponified greases, grease C of Table II and grease K of TableIII.

This example shows that grease products containing the new physicalcombination of soaps of this invention, but containing more than 20%lithium, can be prepared by either cosaponification of the acid using abase containing the desired ratio of lithium to calcium, or by blendingthe desired additional amount of lithium soap with the physicalcombination of soaps after it has been formed by co-saponification.

EXAMPLE 6 Pounds l2-hydroxy stearic acid 237 Mineral oil charged tomixer with .fatty acid 360 Lime 28 Lithium hydroxide 8 Balance ofmineral oil 2089 At 170 F., the following materials were added to impartextreme pressure characteristics to the grease:

Pounds Chlorinated paraflin wax containing 40% chlorine- I 60 Sulfurizedsperm oil 180 Lead naphthenate (containing about 30% lead as PbO) 37.5

The mineral oil used was a mixture of two low cold test mineral oildistillates blended to give a viscosity at 210 F. of 110 SUS. One oil inthe blend had a viscosity at 210 F. of 170/190 SUS, while the other oilhad a viscosity at 210 F. of 53/57 SUS. The composition andcharacteristics of this grease are summarized below.

Composition, percent by weight:

IZ-hydroxyv stearic acid 7,90 Lithium hydroxide 0.27 Hydrated lime 0.94Distillate 170/190 57.00 Distillate 53/57 24.64 Chlorinated wax (40% Cl)2.00 Lead naphthenate 1.25

Sulfurizcd sperm oil 6.00

' invention.

Inspections:

Mineral oil viscosity at 210 F., SUS Worked penetration 305 Droppingpoint, F. "i 312 Timken O.K. load (lbs) 43 Bleeding testl: percent oilloss-100 hrs. at

225 F. 3.9 Water wash test at FF: percent grease loss 12 1 grams ofgrease in a 28 mesh galvanized cone. 2 AN-G. 15 specification.

Conventional animal, vegetable, mineral or synthetic oils can be used toform the grease compositions of this Examples of the latter aredi2-ethyl hexyl sebacate, silicone oils, phosphonates, and complexsynthetic esters formed from alcohols, dicarboxylic acids and glycols.referably the oils used have a viscosity in the range of 10 to 200 SSUat 210 F. and a viscosity index in the range of 30 to 140. It ispreferred to use 12- hydroxy stearic acid as an initial ingredient, butequivalent materials that yield the acid under the saponificationconditions can also be used. For example, esters of the acid that yieldalcohols boiling above 315 F. can be used as a source of the acid. Thetotal soap content of the greases of this invention can range from 5 to15 wt. percent, and the physical combination of soaps can cornprise from75 to 100% of the grease thickener. The preferred grease compositions ofthis invention have a dropping point above 320 F. and a workedpenetration in the range of 300 to 360.

Having described this invention, what is sought to be protected byLetters Patent is succinctly set forth in the following claims. 7

What is claimed is:

1. A lubricating grease comprising a major amount of mineral lubricatingoil'and a grease thickening amount of a mixed-metal thickener preparedby co-saponifying in said lubricating oil 12-hydroxy stearic acid withlithium base and calcium base, heating to a temperature of 275 to 315 F.to dehydrate, and cooling to form said grease, wherein the proportion oflithium to calcium base is such that said mixed-metal thickener consistsof 18 to 22 wt. percent lithium 12-hydroxy stearate and 82 to 78 Wt.percent of calcium 12-hydroxy stearate.

2. A lubricating grease comprising a major amount of mineral lubricatingoil and a grease thickening amount of a soap thickener to forma finalgrease wherein 15 to 25% of the total soap present is lithium 12-hydroxystearate and the remainder of said soap is mixed lithiumcalcium12-hydroxy stearate which is prepared by cosaponifying in a minerallubricating oil IZ-hydroxy stearic acid with lithium and calciumhydroxide, heating to a temperature of 275 to 315 F. to dehydrate tothereby form a mixed calcium-lithium 12-hydroxy stearate grease, theproportion of lithium hydroxide to calcium hydroxide being such thatsaid mixed calcium-lithium 12-hydroxy stearate consists of 18 to 22whpercent lithium 12-hydroxy stearate and 82 to 78 wt. percent ofcalcium 12- hydroxy stearate, mixing with said calcium-lithium 12-hydroxy stcarate grease a second grease comprising mineral lubricatingoil thickened to a grease consistency with lithium 12-hydroxy stearate.

3. A lubricating grease prepared by co-saponifying in minerallubricating oil lZ-hydroxy stearic acid with a lithium base and calciumbase, heating to a temperature within the range of 275 to 315 F. todehydrate, and cooling to form said grease, wherein said lubricating oilhas a viscosity of 10 to 200 SSU at 210 F. and a viscosity index of 30to 140, wherein the amount of lithium to calcium base is such as toresult in a thickener consisting of 20% lithium 12-hydroxy stearate and80% calcium l2-hydroxy stearate, said lubricating grease having 12,929,782 9 10 a dropping point above 320 F. and a work penetration2,607,735 Sproule et a1. Aug. 19, 1952 at 77 F. of 300 to 360 mm./10. 1

OTHER REFERENCES References Cited m the me of thls patent TheManufacture and Application of Lubricating UNITED STATES PATENTS 5Greases, Boner, Reinhold Pub. Corp., New York, 1954, 2,397,956 FraserApr. 9, 1946 pp. 599 and 600. 2,542,159 Stevens- Feb. 20, 1951

1. A LUBRICATING GREASE COMPRISING A MAJOR AMOUNT OF MINERAL LUBRICATINGOIL AND GREASE THICKENING AMOUNT OF A MIXED-METAL THICKENER PREPARED BYA CO-SAPONIFYING IN SAID LUBRICATING OIL 12-HYDROXY STEARIC ACID WITHLITHIUM BASE AND CALCIUUM BASE, HEATING TO A TEMPERATURE OF 275* TO315*F. TO DEHYDRATE, AND COOLING TO FORM SAID GREASE, WHEREIN THEPORPORTION OF LITHIUM TO CALCIUM BASE IS SUCH THAT SAID MIXED-METALTHICKENER CONSISTS OF 18 TO 22 WT. PERCENT LITHIUM 2-HYDROXY STEARATEAND 82 TO 78 WT. PERCENT OF CALCIUM 12-HYDROXY STERATE.